A technique for manufacturing a thin film transistor (TFT) by using polycrystalline silicon using a glass as a substrate that has been crystallized by laser annealing has been developed. A barium borosilicate glass, an aluminosilicate glass, or the like whose distortion point is equal to or less than 700° C. is used as the material of the glass substrate for this use. Accordingly, the maximum temperature acceptable in TFT manufacturing process is equal to or less than the distortion point such that a glass substrate may not be deformed. The importance of laser annealing or rapid thermal annealing (RTA) technique increases as silicon crystallization or an activation treatment of donor or acceptor impurities added into silicon. RTA is a heat treatment technique for heating instantly within several microseconds to several tens seconds and for annealing with electromagnetic wave radiated from a halogen lamp or the like, within the range of from the visible-light region to the infrared light region.
As for silicon film crystallization, there is a case where an amorphous silicon film is directly irradiated with laser light for crystallization. Further, as another mode, there is a technique for improving properties of a gate insulating film as well as enhancing silicon crystallinity by forming the gate insulating film on an island-like crystalline silicon film and then performing laser annealing (For example, Patent Literature 1).
Further, there is a method for accumulating heat in a metal layer formed between a glass substrate and a polycrystalline silicon film for the sake of effectively utilizing heat of RTA, as a technique for activating n-type impurity added into the polycrystalline silicon film over the glass substrate (For example, Patent Literature 2).
On the contrary, in response to miniaturization of a semiconductor element, a flash lamp anneal apparatus is developed, which has a flash lamp using gas plasma as a heat source, and the flash lamp anneal apparatus can raise temperature more rapidly than RTA apparatus using a tungsten halogen lamp as a heat source. The flash lamp anneal apparatus has been improved, particularly, in such a way that it can be applied to formation of a shallow diffusion region that is necessary for a MOS transistor whose gate length is equal to or less than 0.1 μm (For example, Patent Literature 3).
[Patent Literature 1]
Japanese Patent Laid-Open No. Hei 7-321335. (pp. 4–5. See FIG. 1)
[Patent Literature 2]
Japanese Patent Laid-Open No. 2001-102585. (pp. 5–6. See FIG. 1)
[Patent Literature 3]
Japanese Patent Laid-Open No. 2002-246328. (pp. 4–6. See FIG. 1)